Ducts and conduits are used to convey air in building heating, ventilation and air conditioning (HVAC) systems. Often these ducts are formed of sheet metal and as a result do not possess good thermal or acoustical insulating properties. In order to enhance these insulation properties, sheet metal ducts are often insulated using mineral fiber insulation board which is installed around the metal ducts. The insulation board is often manufactured to include a facing material which acts as a vapor retarder/air barrier. Such facing material may be, for example, a FSK (foil/scrim/kraft) facing, a PSK (poly/scrim/kraft) facing, or an ASJ (all-service jacket) facing. In some applications, especially where the ducts or plenum will be subjected to outdoor exposure, a weather-resistant glass fabric and mastic coating is applied to the mineral fiber board insulation that has been installed onto the duct or plenum exterior.
Referring to FIG. 1, a prior art insulated duct 10 is shown having a rectangular duct 20, a mineral fiber insulation board 22, a facing material 24, a glass fabric 26 and a mastic coating 28.
The mineral fiber insulation board 22 is commonly composed of glass fibers bonded together with a thermosetting resin. The insulation board 22, is faced with a facing material 24, such as FSK (foil/scrim/kraft), PSK (poly/scrim/kraft) or ASJ (all-service jacket) to act as an air barrier/vapor retarder. A mastic coating 28 reinforced with a glass fabric or mesh 26 is applied to the facing material 24 to supply a weather barrier.
Typically, where a weather barrier is to be applied, a first coat of the mastic coating 28 is brushed, troweled or sprayed onto the facing material after the faced insulation board has been installed over the duct 20. The glass fabric 26, which is typically provided in the form of a roll, is cut to the proper dimensions and embedded into the first coat of the mastic coating 28. After embedding the glass fabric 26, a second coat of the mastic coating 28 is brushed, troweled or sprayed onto the glass fabric 26 to continuously cover the faced insulation board with the glass-reinforced mastic coating.
The process of having to cut and fit the glass fabric at the installation site is fairly labor-intensive and thus adds costs to the building project.
What is needed is an improved insulation product and method for installing the insulation product around ducts.